Miyota Caliber 1M12

Manufacturer	Miyota (Citizen)
Caliber Number	1M12
Type	Quartz
Replacement Caliber	GM10
Lignes	10.5”’
Diameter	23.7mm x 22.6mm
Height	2.71mm thick
Battery Cell Number	363 / 364 (SR621SW)
Battery Life	~3 years
Jewel Count	0
Frequency	32,768Hz
Quartz Type	Tuning fork type quartz crystal
Stem	065-505 (tap 10)
Hand Sizes	1.20mm / .70mm / .17mm
Driving System	Two-pole stepping motor
Hacking Seconds?	Yes
Hand Count	3
Functions	Central hours; central minutes; central seconds; date calendar at 3:00
Country of Manufacture	Japan
Known Models	Android Mantis (Add your watch to the comments below…)

The Miyota caliber 1M12 is part of the 1L/1M family of affordable quartz calibers. The 1M12 is a 0 jewel quartz movement that is made in Japan. Although you can still find this caliber for sale, it has since been replaced by the Miyota caliber GM10 or GM12.

1M12 VS 1M02:

Miyota makes a similar caliber 1M02. The main difference when comparing the two is that the 1M02 also has a bilingual day of the week complication. Therefore, the 1M12 is a date movement and the 1M02 is a day-date movement.

1M12 VS 1L12:

There is a 1L12 that is basically the same as the 1M12, except that it is smaller in size. The 1L12 is 15.3mm x 18.2mm compared to the 1M12 at 23.7mm x 22.6mm.

1M12 Accuracy Rating:

Miyota states the accuracy of this movement to be +/-20 seconds/month when “worn under normal circumstance”.

Battery Cell:

The cal. 1M12 takes an SR621SW (364) watch battery. The battery is said to last up to 3 years. There is a battery saving (aka hacking) mode by pulling out the stem into time setting mode (position II). When doing this, the seconds hand will stop and the power consumption will be limited. Below is a view of the empty battery tray. No insulator film is necessary since the base is plastic.

Replacement Price:

At the time of this post the replacement price of a new Miyota calibre 1M12 is around $7 – $9.50 USD.

Interchangeability:

The good thing about the small, cheap Miyota movements is that they can usually be interchanged with similar calibers (eg: Miyota 20XX / 21XX / 6LXX / 6MXX) if you can’t find a replacement, or if you want to add or remove additional features to modify an existing watch.

Examples of watches with this movement:

The movement pictured below was found in this Android Mantis model AD499, as shown below with the black plastic movement holder removed from the case. For this watch, Android opted to remove the seconds hands, making it a 2-hander with a date.

Additional Resources:

• List of Miyota movements